The present inventions relates to a sailboat of the type normally referred to as a trimaran, having a main hull with smaller starboard and port hulls on either side thereof. Such sailboats conventionally include one or more masts mounted on the main hull with shrouds often fixed at or near the rail of the side hulls. Such sailboats normally have very good sailing properties, particularly for ocean racing, since a great stiffness relative to weight is obtained with the three-hull configuration. A great initial stiffness gives a smaller inclination, and thus better comfort. Further, such a construction allows each hull to be designed without requiring that it remain stable, allowing use of narrow hulls with low resistance. The bottoms of the side hulls are conventionally positioned vertically above the main hull bottom so that when the sailboat is upright with the wind from the stern, or in light winds, the boat sails on the main hull alone, thereby providing low resistance. Since no ballast is necessary, the trimaran also can be made unsinkable.
While trimarans have many advantages, there is one significant drawback associated with conventional trimarans. A conventional trimaran reaches its greatest stability at 20.degree.-35.degree. inclination, and at larger inclinations the stability steadily decreases down to zero at about 80.degree. inclination. Thus, trimarans can capsize due to the impact of wind or waves, and are not self-righting, so that once capsized they remain upside down.
Various proposals have been suggested in the art for minimizing the adverse consequences associated with a trimaran's lack of self-righting ability. For instance, in Swedish Pat. No. 383,497, a trimaran with safety rigging is proposed which provides a mast which can move relative to the main hull. However, the movable mast alone does not lower the risk of capsizing due to waves.
In French Pat. Nos. 1,505,692 and 1,574,766 proposals are made for mounting the starboard and port hulls so that they are movable relative to the main hull. While such an arrangement provides better stability, sailing comfort in very hard winds is relatively poor, and stability still is not as good as desired.
According to the present invention, a trimaran is provided that overcomes the stability and other problems associated with conventional trimarans and the prior proposed trimarans discussed above. The trimaran according to the present invention is self-righting, and the angle of inclination of the main hull is minimized. In fact, positive stability of the trimaran according to the present invention is provided up to about 130.degree. inclination of the main hull, compared to 80.degree. inclination of the main hull for conventional trimarans.
According to the trimaran of the present invention, means are provided for operatively attaching the starboard and port hulls to the main hull so that each of the starboard and port hulls is pivotal with respect to the main hull about an axis generally parallel to the direction of elongation of the main hull. Further, means are provided for pivotally mounting the mast to the main hull so that the mast is pivotal about an axis substantially parallel to the axes about which the starboard and port hulls are pivotal, and shroud means are provided for operatively attaching the mast to the starboard and port hulls. At least one spring device is pivotally connect at one end thereof to the main hull and at the other end thereof to the each of the starboard and port hulls, and a stop means is provided for stopping the movement of the starboard or port hulls towards the main hull at a predetermined desired position. The force applied by the spring devices are of sufficient magnitude to prevent substantial pivotal movement of the starboard and port hulls with respect to the main hull in normal fresh winds, while such pivotal movement is allowed in winds stronger than normal fresh winds. If desired, a resilient device may be operatively attached to each shroud, such as between the shroud and the side hull with which it is associated, to allow variation in the length thereof during relative movement of the mast with respect to the main hull.
In actual comparative testing, and in comparative mathematical analyses, of the trimaran according to the present invention and conventional and prior proposed trimarans, the trimaran according to the present invention has greatly improved stability and sailing comfort, and such stability and sailing comfort are achieved with a relatively minimal increase in the cost of construction.
It is the primary object of the present invention to provide a trimaran with maximum stability. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.